CVE-2017-5435 in Firefox
Summary
by MITRE
A use-after-free vulnerability occurs during transaction processing in the editor during design mode interactions. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.1, Firefox ESR < 45.9, Firefox ESR < 52.1, and Firefox < 53.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability described in CVE-2017-5435 represents a critical use-after-free condition that manifests during transaction processing within the editor component of Mozilla's browser and email applications. This flaw occurs specifically when users interact with the editor in design mode, creating a scenario where memory previously allocated to objects becomes accessible after the object has been freed, leading to unpredictable behavior and potential exploitation. The vulnerability affects multiple Mozilla products including Thunderbird, Firefox ESR, and standard Firefox releases, indicating a widespread impact across the Mozilla ecosystem.
The technical nature of this vulnerability aligns with CWE-416, which defines use-after-free conditions as a common class of memory safety issues where programs continue to reference memory locations after they have been freed by the system. During normal operation, the editor component manages transaction processing that involves complex object manipulation and memory allocation. When design mode interactions occur, the system fails to properly manage object lifecycles, creating opportunities for attackers to manipulate freed memory locations. This memory corruption can result in application crashes, which in this case could be leveraged to execute arbitrary code through carefully crafted input that triggers the vulnerable code path.
The operational impact of this vulnerability extends beyond simple application instability, as it presents a potential attack vector for remote code execution. Attackers could exploit this condition by crafting malicious content that when processed by the vulnerable applications would trigger the use-after-free scenario. The crash conditions that result from this vulnerability could be manipulated to overwrite memory contents or redirect execution flow, particularly when combined with other exploitation techniques. The affected versions span multiple release channels including extended support releases, indicating that organizations using these versions would be at risk for extended periods without patching.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected systems to the latest available versions, as Mozilla released security updates addressing this specific issue. Organizations should implement network segmentation and access controls to limit exposure of vulnerable systems, while also considering browser hardening techniques such as address space layout randomization and stack canaries. Security monitoring should focus on detecting anomalous application behavior that might indicate exploitation attempts, particularly around editor component usage and transaction processing activities. The vulnerability demonstrates the importance of thorough memory management practices in complex software components and highlights the need for comprehensive security testing of interactive user interface elements that handle dynamic content processing. This flaw serves as a reminder of the critical importance of maintaining up-to-date security patches across all software components, particularly those handling user input in rich text editing environments.